This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. xc2xa7119 from my application PAPER SORTING DEVICE FOR IMAGE FORMING APPARATUS filed with the Korean Industrial Property Office on Dec. 29, 2000 and there duly assigned Ser. No. 86384/2000.
1. Technical Field
The present invention relates to an image forming apparatus such as a laser printer and, more particularly, to a paper sorting device for an image forming apparatus capable of sorting printed paper sheets in a zigzag pattern.
2. Related Art
A laser printer is one of the major image forming devices for printing desired data on paper sheets page by page while being connected to a computer network. Unlike the conventional dot printer or ink jet printer, the laser printer uses an electronic photoprinting method which projects a laser beam onto a charged photosensitive medium to form an electrostatic latent image, develops the electrostatic latent image into a visible image by means of toner particles, and transfers and fixes the visible image on paper.
Typically, a laser printer has a paper cassette, a developing unit, a built-in duplex printing unit, a stacker, and a distributing unit.
In operation, a sheet of paper is picked up from the paper cassette, is fed to and printed in the developing unit, is passed through the distributing unit, and is stacked on the stacker. In duplex printing, paper printed by the developing unit is fed from the distributing unit to the duplex printing unit, and is returned to the developing unit according to a predetermined paper feeding route of the duplex printing unit. A non-printed side of the returned paper is printed by the developing unit, is passed through the distributing unit, and is stacked on the stacker.
In a conventional laser printer, the paper which is printed through a series of processes, as described above, is consecutively stacked on the stacker. Since the paper is consecutively stacked on the same spot in the stacker, a user has to manually sort the paper for distribution, especially when the same image is multi-printed. Manual sorting of the paper causes inconvenience and loss of time to the user.
The present invention has been developed to solve the above-mentioned problem. Accordingly, it is an object of the present invention to provide a paper sorting device for an image forming apparatus capable of automatic sorting of printed paper sheets in a simple and economical manner.
To accomplish the above object, the paper sorting device of the present invention comprises a rotating shaft rotated by a driving force from a driving force source, a hollow shaft to which the rotating shaft is slidably inserted, the hollow shaft being rotated with the rotating shaft and reciprocated on the rotating shaft, and reciprocating means for reciprocating the hollow shaft.
The hollow shaft has a plurality of guide slits formed in its interior, the rotating shaft has a plurality of rails formed on an outer circumference and corresponding to the guide slits of the rotating shaft, and the hollow shaft is rotated as a result of the rotation of the rotating shaft and is reciprocated on the rotating shaft. The hollow shaft also has a plurality of rollers formed on its outer circumference, the rollers contacting the paper.
The reciprocating means comprises a driving shaft disposed in parallel with the rotating shaft at a predetermined interval for engaging and rotating with the rotating shaft, a guide block connected to one end of the hollow shaft, and also connected to a guide rail on a lower portion thereof, the guide block being reciprocated along the guide rail so as to reciprocate the hollow shaft, a guide cam disposed in the driving shaft and having a guide groove of a certain pattern formed on its outer circumference, a guide lever having one end hinged on an upper portion of the guide block and another end inserted in the guide groove, and a clutch for selectively transmitting the rotating force of the rotating shaft to the driving shaft. The guide groove is formed on the outer circumference of the guide cam and has a helical shape.
The clutch comprises a sector gear disposed around the driving shaft and selectively connected to a driving gear on an upper end of the rotating shaft, a stepping cam disposed around the driving shaft and in parallel with the sector gear, the stepping cam having a stepped portion on an outer circumference thereof, a stopper contacting the stepped portion for restricting rotation of the stepping cam, a solenoid causing the stopper to contact the stepped portion or release the contact, an oval cam disposed around the driving shaft and in parallel with the stepping cam, a lever for pressing and contacting the oval cam, and a spring biasing the lever toward the oval cam.
The paper sorting device further comprises a detector for detecting the left and right positions of the hollow shaft. The detector comprises a photosensor disposed in the image forming apparatus, an eccentric cam disposed around the driving shaft, and a sensing shaft having one end which has a lever in contact with an upper portion of the eccentric cam and another end which has an optic cutoff lever, the optic cutoff lever selectively cutting off light transmitted between a light generating part and a light receiving part of the photosensor by reciprocating with the rotation of the eccentric cam.
According to the present invention, printed paper is ejected by the reciprocating movement of the hollow shaft having rollers, and the paper is automatically sorted in a zigzag pattern.